Stop the Tears: Why Onions Are Good for You, Reveals Nutritionist

Few kitchen experiences are as universal—and frustrating—as the sting of chopping onions. That sharp, involuntary blink… the nose that starts to tickle… and those inevitable tears. But have you ever wondered why onions hit your tear ducts harder than most vegetables? And more importantly, is there more to this humble bulb than just its sob-inducing chemistry?

Here’s what’s really happening: when you slice into an onion, you’re triggering a defensive chemical reaction. Inside those crisp white layers are sulfur-containing compounds, and one in particular—syn-Propanethial-S-oxide—is the culprit. Once released, this compound vaporizes into the air and heads straight for your eyes, where it interacts with the water on the surface. This reaction forms a mild sulfuric acid, and your brain quickly responds by stimulating your tear glands to flush the irritation away.

The impact is immediate. Suddenly you’re sniffling over your cutting board, pausing to rub your eyes (not recommended, by the way), or reaching for a tissue as your dinner prep grinds to a watery halt. It’s no wonder so many people dread this part of cooking—complaints range from ruined mascara and irritated contact-lens wearers to complete abandonment of the recipe mid-chop.

But here’s the twist: that same compound that brings the sting also delivers surprising health benefits. So instead of tossing out that onion in frustration, let’s explore why it’s time to stop the tears—and start appreciating what onions are really made of.

Understanding Onions as a Functional Food

More Than Just a Flavor Enhancer

Think of onions, and what probably comes to mind first is their bold, tear-inducing flavor. But behind that pungent punch lies a vegetable with remarkable functional properties. Far beyond their role in stews and stir-fries, onions act as a natural medicine cabinet. They offer health benefits that stand up to scientific scrutiny, turning an everyday ingredient into a powerful ally for long-term wellness.

Onions as a Medicinal and Nutritional Vegetable

Onions don’t just support health; they actively enhance it. For centuries, cultures around the world have used them in traditional medicinal systems—from Ayurveda to Traditional Chinese Medicine—to treat everything from coughs to infections. Today, research backs up many of these applications. Multiple studies show that onions possess antibacterial, antidiabetic, anticancer, and cardiovascular-protective properties, making them a multi-talented food with real impact.

Functional Nutrient Compounds

What gives onions their functional edge? A potent mix of phytochemicals and sulfur-containing compounds. The standout is quercetin, a flavonoid with powerful antioxidant and anti-inflammatory properties. According to a 2019 review published in Food & Function, quercetin modulates blood pressure and supports endothelial function, critical for heart health.

Another key player is organosulfur compounds, which form when the onion is chopped or crushed. These compounds are responsible for both the pungent aroma and the plant’s remarkable bioactivity. Allicin, although more prominent in garlic, also appears in onions and has been shown to inhibit bacterial growth and support detoxification pathways in the liver.

Rich in Essential Micronutrients

Besides their bioactive compounds, onions deliver a range of essential nutrients that many people overlook.

• Vitamin C: A medium-sized raw onion provides around 12% of the daily recommended intake. This vitamin boosts immune function and supports collagen production for skin and joint health.
• Vitamin B6: Critical for neurotransmitter synthesis and cognitive function. Onions contribute modestly to daily intake, supporting brain and energy metabolism.
• Folate (B9): Necessary for DNA synthesis and repair. Particularly important for pregnant women, folate levels can be gently supported by incorporating onions regularly.
• Manganese: A trace mineral involved in antioxidant enzyme function and bone formation. Onions provide a plant-based source that complements a balanced diet.

Each of these micronutrients works in synergy with the phytochemicals present in onions, enhancing their overall effect and making them a genuinely functional food.

When was the last time you looked at an onion and thought: “medicine in disguise”? The next time you chop one, remember—those tears may be just the beginning of something much more powerful.

Nutritional Value of Onions: A Low-Calorie, High-Impact Food

Onions might seem like a simple kitchen staple, but their nutritional profile tells a more impressive story. Behind their humble appearance lies a powerhouse of nutrients, all packed into a vegetable that’s low in calories and high in impact.

Macronutrients and Micronutrients: What You’re Really Eating

Per 100 grams, raw onions deliver about 40 calories, making them an excellent addition to any diet focused on nutrient density. Their macronutrient composition includes:

• Carbohydrates: Approximately 9.3 grams, with a natural sweetness that intensifies when cooked.
• Proteins: About 1.1 grams, modest but useful in plant-based diets.
• Fats: Negligible, making them virtually fat-free.

Micronutrient-wise, onions supply a surprising variety. They’re a modest source of vitamin C (roughly 7.4 mg per 100 grams), which supports collagen production and defenses against oxidative stress. You’ll also find small, yet effective, amounts of B vitamins like vitamin B6 and folate, supporting metabolism and red blood cell formation. Potassium stands out among minerals at roughly 146 mg per 100 grams, contributing to electrolyte balance and cellular function.

Fiber, Antioxidants, and Trace Minerals: Small Pieces, Big Impact

One of the lesser-appreciated aspects of onions is their fiber content. A single medium onion provides about 1.7 grams of dietary fiber, much of it prebiotic in nature, particularly in the form of inulin. Prebiotics fuel the growth of beneficial gut bacteria, which, in turn, supports immunity and digestion.

They’re also a source of flavonoid antioxidants, notably quercetin and kaempferol. These compounds reduce oxidative damage and show potential in improving vascular function. Trace minerals like manganese, copper, and chromium play metabolic support roles, from enzymatic activity to blood sugar regulation.

Calories and Serving Sizes: High Nutrient Density, Minimal Load

A typical serving—about 1 cup of chopped raw onion (roughly 160 grams)—delivers only around 64 calories. That’s a small caloric load for the level of health-supporting compounds you’re getting. Whether chopped raw into a salad or caramelized into a dish, onions add volume, texture, and nutrients without tipping the calorie scale.

Water Content: Hydrating, and It Shows

Surprisingly high in water, onions average about 89% water content. This makes them refreshing and hydrating, which contributes to their low calorie density. The water also enhances satiety, meaning you can add bulk to meals while keeping overall energy intake low—a key factor in weight management strategies.

Next time you’re dicing a bulb, think beyond flavor and tears. You’re adding hydration, fiber, vitamins, and powerful antioxidants—on a budget of just a few dozen calories per serving. Not bad for a humble allium, right?

The Antioxidants in Onions: Powerhouse of Cellular Protection

Behind every chopped onion—and the tears that follow—is a remarkable antioxidant profile that gives this humble vegetable its protective edge. These antioxidants actively defend your body’s cells against oxidative stress, a key factor in aging and disease development. Let’s unpack the antioxidant arsenal packed within each layer.

Quercetin: A Shield for Your Cells

Quercetin stands out as one of the most potent antioxidants found in onions, especially concentrated in the outer layers of yellow and red varieties. It’s a flavonoid known not only for neutralizing free radicals but also for interrupting the chain reactions that damage cellular structures.

Multiple studies highlight quercetin’s wide-ranging effects. One clinical trial published in the European Journal of Clinical Nutrition demonstrated that a daily intake of quercetin-rich foods significantly reduced biomarkers of oxidative stress in healthy adults. In practical terms, when you chop onions into your salad or sauté them into your soup, you’re reinforcing your body’s internal defense system with every bite.

This compound performs double duty—it fights oxidative stress while also modulating inflammation, paving the way for long-term health benefits, especially in metabolic and cardiovascular systems.

Anthocyanins: The Red in Red Onions Does More Than Look Pretty

Red onions aren’t just visually striking—they deliver unique health benefits thanks to anthocyanins, the pigments that create their deep, purplish hue. These natural compounds have strong antioxidant and anti-inflammatory actions.

Research published in the journal Food & Function showed that anthocyanins contribute to protecting the vascular system by improving endothelial function and reducing oxidative stress markers in blood vessels. This means that red onions function as more than a garnish—they actively support heart health with measurable precision.

Beyond the heart, anthocyanins also contribute to brain and eye health by shielding sensitive tissues from free radical damage. Incorporating red onions into your diet adds a layer of neurological and visual protection that colorless onions don’t offer as strongly.

How Do Onions Stack Up? Their Overall Antioxidant Power

Onions consistently rank high on the antioxidant scale compared to other vegetables, and that’s not just anecdotal evidence. The Oxygen Radical Absorbance Capacity (ORAC) score—a measure developed by the USDA to evaluate antioxidant power—places onions above several widely consumed vegetables.

• Yellow onions score approximately 450 ORAC units per 100 grams.
• Red onions, enriched with both quercetin and anthocyanins, reach up to 600 ORAC units.
• In contrast, cucumbers and iceberg lettuce fall below 100 ORAC units, making onions a far more effective option for boosting antioxidant intake.

Antioxidants from food sources like onions don’t just combat damage; they also enhance enzyme function and support repair mechanisms within the body. By integrating onions into your daily meals—raw or cooked—you’re building a layer of cellular protection that accumulates over time.

Next time you slice an onion and your eyes start to sting, take a moment to appreciate what you’re really doing: arming your body with some of nature’s most powerful chemical defenders.

No More Sneezing Seasons: How Onions Bolster Your Immune System

Your immune system is your body’s first line of defense—and onions do more than just add flavor to your meals. They deliver a unique cocktail of nutrients, compounds, and fibers that directly and indirectly support immunity. Each layer of an onion packs more than just pungency; it offers scientifically-backed immune-boosting benefits that deserve a closer look.

Vitamin C: Essential Fuel for Immune Function

Onions are surprisingly rich in vitamin C, a key player in maintaining a resilient immune defense. This antioxidant vitamin supports multiple cellular functions of both the innate and adaptive immune system. It enhances the barrier function of the skin, helps neutralize pathogens, and promotes the proliferation and function of white blood cells, especially phagocytes and T-cells.

According to the National Institutes of Health, vitamin C contributes to the body’s defense by increasing the production and function of lymphocytes—white blood cells that target harmful invaders. A 100-gram serving of raw onion provides roughly 8% of the daily recommended intake of vitamin C. While onions aren’t the richest source, they offer a steady, complementary supply when combined with other whole foods in a varied diet.

Super-Charged White Blood Cells

What happens inside your immune system when you eat onions? One of the more fascinating effects involves the support of white blood cell activity. Scientific evidence suggests that the flavonoids in onions—particularly quercetin—enhance the response of immune cells by protecting them from oxidative stress and supporting signaling pathways involved in immune regulation.

A 2016 review in Nutrition Reviews found that flavonoids can up-regulate the expression of immune-related genes and increase the activity of natural killer cells. These cells play a critical role in containing viral infections during the early stages—and onions, rich in quercetin, contribute to strengthening these responses.

Prebiotic Fiber: Fueling a Healthier Gut, and a Stronger You

More than 70% of your immune system activity originates in your gut. Onions contain prebiotic fibers, especially inulin and fructooligosaccharides (FOS), which selectively feed beneficial gut bacteria like Bifidobacterium and Lactobacillus. These bacteria thrive on these fibers and, in return, produce short-chain fatty acids (SCFAs) that modulate immune response.

Numerous studies, including a 2017 review in Microbial Pathogenesis, confirm that dietary intake of prebiotics results in a more balanced gut microbiome, reduced systemic inflammation, and protection against pathogens. When the gut is in balance, your immune system functions more efficiently. Incorporating onions regularly is a direct way to make that happen.

Natural Antimicrobial Warriors

Need help fending off minor infections? Onions may lend a hand here too. Packed with natural antimicrobial compounds, onions have been shown to inhibit the growth of various pathogens, including Escherichia coli, Staphylococcus aureus, and Salmonella typhimurium. These effects are largely attributed to their sulfur-containing compounds and flavonoids.

Allicin, a sulfur-based compound formed when onions are chopped or crushed, exhibits strong antibacterial and antifungal activities. According to research published in the Journal of Antimicrobial Chemotherapy, allicin disrupts bacterial cell membranes and interferes with enzyme activity, making it harder for harmful microbes to persist in the body.

So next time you’re building your plate, consider this: every slice of onion doesn’t just add crunch—it adds immune resilience, from gut to cells to skin.

Blood Sugar and Onions: A Sweet Benefit

When it comes to managing blood sugar, onions are a surprisingly powerful ally. Their delicate balance of complex carbohydrates, fiber, and biologically active compounds makes them more than just a flavorful addition—they’re a functional food with real metabolic benefits.

Onions in Blood Sugar Regulation

Onions contain key compounds like quercetin and sulfur-based antioxidants, which have demonstrated blood sugar-lowering effects. These compounds influence how the body metabolizes glucose and support better glycemic control. One particular bioactive—the flavonoid quercetin—enhances glucose uptake in peripheral tissues while inhibiting enzymes such as α-glucosidase that break down carbohydrates too quickly. This slows the release of sugars into the bloodstream and preserves insulin balance.

Moreover, the chromium content in onions plays a notable role in enhancing insulin activity, improving the efficiency with which cells absorb glucose. Chromium works at the receptor level, fine-tuning insulin signaling and helping the body respond more effectively to the hormone.

Effects on Insulin Sensitivity and Glycemic Control

The daily inclusion of onion in the diet directly supports insulin sensitivity. In controlled human trials, individuals with type 2 diabetes who consumed 100 grams of fresh red onion daily showed significantly reduced fasting blood glucose levels after four hours. Researchers observed drops of up to 40 mg/dL, confirming onions’ acute impact on glucose metabolism.

Animal studies offer further insight. Rats fed diets supplemented with onion extracts exhibit improved glucose tolerance and lower insulin resistance markers. These studies also reveal improvements in hepatic enzyme activity, which supports long-term stability in blood sugar levels by improving glucose handling in the liver.

Role in Diabetic Diets

With a glycemic index (GI) of around 10–15, onions classify as a low-GI food. This makes them particularly suitable for diabetic meal planning where glycemic impact must be minimized. Because they digest slowly, they reduce postprandial spikes and contribute to sustained energy levels—an often overlooked yet critical piece in type 2 diabetes management.

Their fiber—specifically the soluble type like inulin—furthers metabolic balance. Inulin bypasses enzymatic digestion in the upper gut and is fermented in the colon, creating short-chain fatty acids that improve insulin signaling and appetite regulation.

Supporting Studies

• Journal of Medicinal Food (2010): A clinical trial found that raw onion consumption significantly lowered blood glucose levels in both normoglycemic and diabetic patients within a few hours of ingestion.
• Pakistan Journal of Pharmaceutical Sciences (2015): Researchers demonstrated improved insulin sensitivity in diabetic rats given onion extract daily over eight weeks, with marked decreases in HbA1c and improved lipid profiles.
• Nutrition & Metabolism (2017): A randomized study observed meaningful improvements in fasting blood sugar and LDL cholesterol after eight weeks of dietary onion supplementation in overweight adults with metabolic syndrome.

These results point to a clear truth: onions aren’t just about flavor—they serve as a dietary tool to regulate glycemia, enhance insulin work, and strengthen metabolic resilience.

Stop the Swelling: The Anti-inflammatory Power of Onions

Chronic Inflammation: A Root Cause of Many Diseases

Low-grade, chronic inflammation doesn’t always scream for attention, but it steadily contributes to health issues like arthritis, asthma, cardiovascular disease, and even diabetes. The body’s natural defense mechanism, when left unchecked, can turn into the enemy—fueling flare-ups and discomfort that wear the body down over time. What if a simple staple like the onion could interrupt this cycle?

How Onions Help with Arthritis, Asthma, and Gut Inflammation

Daily consumption of onions offers a steady supply of compounds that help modulate inflammatory responses. In patients with rheumatoid arthritis, low-grade systemic inflammation often results in stiff, swollen joints. Onions, rich in flavonoids such as quercetin, can significantly reduce levels of pro-inflammatory cytokines like TNF-α and interleukin-6 (IL-6), both of which are commonly elevated in arthritic conditions.

Research published in the Journal of Medicinal Food noted that quercetin suppresses markers of inflammation in both animal and human studies, easing symptoms related to arthritis. Meanwhile, people with asthma—characterized by airway inflammation—may benefit from onion’s ability to reduce histamine release and bronchial inflammation. This effect is especially pronounced when onions are consumed raw or minimally cooked, preserving their active compounds.

The gut also reaps the rewards. Onion’s prebiotic fiber combines with its anti-inflammatory compounds to promote a healthier microbiome and reduce intestinal inflammation, making them useful in managing conditions like ulcerative colitis and IBS.

Meet the Bioactive Sulfur Compounds Behind the Relief

Onions belong to the Allium family, a group known for its unique sulfur-rich profile. When you chop an onion, the transformation of sulfur amino acids triggers the release of thiosulfinates, sulfoxides, and especially allicin. These bioactive sulfur compounds don’t just give onions their pungent smell—they act as powerful natural anti-inflammatory agents.

Allicin and its derivatives disrupt the production of nitric oxide and prostaglandins, both of which are inflammatory mediators. A 2020 study in the journal Nutrition & Metabolismconfirmed that sulfur compounds from Allium vegetables modulate key signaling pathways, including NF-κB, a master switch in the inflammatory response.

Onions vs. Other Natural Anti-inflammatories: How Do They Compare?

It’s no secret that turmeric and ginger are heavy-hitters in the world of natural anti-inflammatories. But onions hold their own—and they offer unique advantages. While turmeric’s active compound curcumin targets inflammation at the genetic level, and gingerol in ginger regulates oxidative stress, onions bring a broader anti-inflammatory spectrum with both quercetin and sulfur compounds working in synergy.

• Turmeric: Best for joint inflammation and oxidative stress; requires fat for absorption.
• Ginger: Excellent for muscle soreness and digestive inflammation; often used in teas and extracts.
• Onions: Support systemic inflammation reduction; easily integrated into daily dishes with minimal effort.

Instead of choosing one, combining these foods makes the effects even stronger. Imagine an anti-inflammatory soup infused with onions, turmeric, and fresh ginger—each component amplifying the other’s healing potential. But even on its own, the humble onion works tirelessly. Slice it, sautée it, or serve it raw, and it will continue doing what it does best: helping your body turn down the inflammatory noise.

Ancient Wisdom in Every Layer: Onions in Traditional and Folk Medicine

Long before the scientific community began unravelling the health benefits of onions, cultures around the world had already turned to this pungent bulb for healing. Passed down through generations and deeply embedded in traditional systems, onions weren’t just food—they were frontline medicine. Let’s take a closer look at how onions earned their status as a household remedy and how contemporary research reflects the wisdom of the past.

Historical Uses Across Civilisations

In Ancient Egypt, onions symbolised eternity. Tomb paintings and archaeological findings suggest that onions were not only part of the diet but also used in mummification. They believed the strong scent and spherical layers had mystical life-giving qualities. Workers who built the pyramids were regularly fed onions, garlic, and radishes to increase stamina and prevent illness.

In Traditional Chinese Medicine (TCM), onions were referred to as “warm” foods. Practitioners used them to disperse cold, stimulate circulation, and relieve nasal congestion. Their application was often combined with ginger and garlic to fortify Wei Qi—the body’s defensive energy.

Ayurveda, India’s ancient system of natural healing, classifies onions as a tamasic food, yet recognises their medicinal value. Onions were used to balance Vata energies due to their grounding, heating, and lubricating properties. They played a key role in treating respiratory issues, reproductive imbalances, and digestive ailments.

Folk Remedies That Stand the Test of Time

Throughout Europe in the Middle Ages, onions were so highly regarded that people used them to pay rent and give as wedding gifts. Yet their real power came through in folk medicine. Onion poultices—warm layers of cooked onion wrapped in cloth—were applied to the chest to relieve congestion or to joints to ease swelling and pain.

Homemade onion cough syrup was a kitchen staple. Sliced onions layered with sugar or honey stood overnight, producing a syrup that soothed sore throats and loosened phlegm. Its effectiveness had roots in the onion’s sulfur compounds, particularly thiosulfinates, known for their antimicrobial properties.

Another age-old application used onions for earaches. Warm onion juice, extracted by gently roasting the bulb, was dropped into the ear canal to alleviate infection or pain. While anecdotal, people swore by its efficacy—and many still do.

Proven Old Wives’ Tales? Aligning Tradition with Science

What’s fascinating is how modern research aligns with these traditional uses. Studies have confirmed onions’ anti-inflammatory, expectorant, and antimicrobial properties—exactly what our ancestors seemed to know instinctively.

• Respiratory support: A 2015 review in Journal of Ethnopharmacology outlined how onion extracts reduced bronchial inflammation and inhibited microbial growth, validating traditional cough and cold remedies.
• Circulatory benefits: Evidence supports the traditional view from TCM that onions aid circulation. A study published in Thrombosis Research found that onion flavonoids, specifically quercetin, improve endothelial function and reduce platelet aggregation.
• Topical healing: Sulfur-rich compounds like allicin offer antifungal and antibacterial action, supporting the historical use of onion poultices for wounds and skin infections.

Centuries of anecdotal wisdom now find grounding in lab results and controlled trials. The healing power of onions doesn’t rest only in legend—it pulses through both tradition and data. So next time you slice into one, remember: you’re engaging with a remedy that’s helped humans thrive for millennia.

Why Onions Are Cry-Worthy—in a Good Way

Chopping onions often leads to stinging eyes and uncontrollable tears—but those fleeting discomforts are a small price to pay given everything this humble vegetable brings to the table. Beyond the kitchen drama, onions stand out as a nutrient-dense, disease-fighting, and flavor-boosting powerhouse. Here’s why watery eyes today can mean a healthier tomorrow.

A Layered Treasure of Health Support

Onions aren’t just a culinary staple—they’re a textbook example of food as functional medicine. From cardiovascular support to anti-inflammatory action, their health benefits are diverse and well-documented in clinical research.

• Cardiovascular Benefits: A study published in the American Journal of Clinical Nutrition found that quercetin, a major antioxidant in onions, significantly reduces blood pressure in hypertensive individuals.
• Immune System Boost: Onions contain allicin and sulfur compounds that stimulate immune cell efficiency—making your body more resistant to infections.
• Natural Blood Sugar Modulation: Researchers in a 2010 publication in the journal Environmental Health Insights observed a diabetic-friendly effect, where raw red onion consumption lowered fasting blood glucose levels.
• Anti-inflammatory Defense: Onions contain flavonoids and sulfur compounds that actively suppress inflammatory pathways and may help manage conditions like arthritis and asthma.
• Gut Microbiome Support: Inulin, a type of prebiotic fiber found in onions, feeds beneficial gut bacteria and plays a key role in digestive health and immune regulation.

And the benefits don’t stop there. Multiple studies have linked high onion consumption to a reduced risk of several types of cancer, including stomach and colorectal, due to their high content of organosulfur compounds and antioxidants like anthocyanins in red onions.

A Minor Inconvenience for a Major Payoff

Yes, the tears can be annoying. The moment you slice into an onion, sulfur-containing compounds mix with enzymes to produce syn-Propanethial-S-oxide, a volatile gas that irritates the tear glands. But here’s the thing: that same compound—specifically the sulfur—is heavily involved in many of the health benefits you just read about. It’s a trade-off worth embracing.

And guess what? You can have your onions and slice them too—without the waterworks. Use a sharp knife, chill the onion beforehand, and cut with proper ventilation. These simple kitchen tweaks reduce the release of eye-irritating gases without compromising flavor or nutrition.

Time to Get Cooking

Ready to make peace with this tear-worthy vegetable? Choose a dish—perhaps a hearty French onion soup, a spicy onion chutney, or a caramelized onion flatbread—and try it today using one of the anti-tearing techniques we’ve shared. The flavor you’ll unlock is worth every second of prep.

What’s your favorite way to use onions? Do you swear by chilled chopping, or have another anti-tear secret? Share your go-to recipes and kitchen hacks—we’d love to hear how onions find their way into your meals.